Gas and Oil Home Heating Furnaces - Air inlet

My house has three air inlets to the forced air unit. One of them happens to be on the wall that is the best place to put the TV and stereo against. Problem is when the air kicks in, the volume has to be turned way up to watch TV or listen to music. I would like to 'disable' the air inlet and drywall where it used to be and pretend it never existed. Any ideas?

NO! NO! NO! If you block that return air grill then you need to install a return in another location. You need all the return air that you can get.

Can you elaborate on why one of the inlets can't be covered up? There are two other inlets and the one in question is smaller than the other two.

If the concern is the amount of air that the unit can take in, wouldn't the amount of air accepted through the other two compensate for the blocked inlet? All three inlets currently feed into the same duct.

I'm no A/C mech. here, but this is my thoughts. Most units I have seen usually have only one return vent. I would determine the amount of return air needed by your unit and figure if the size of the two vents would allow that much air to be returned. However, before jumping in and sheetrocking over the "bad" vent, I would just cover it with cardboard. This way you could check to see if there are any averse effects it may cause by not having that vent there. There may be a reason it is there, air circulation in that room may be bad. The loss of this vent could make the room uncomfortable to be in, to hot/cold.
Is noise your hear from the blower? Is there a quieter motor or fan assembly you might be able to install?